Hiya Jeremy, I am really sorry for the delay in responding to you – and I thank you for your offer of help. Today I figured out what was wrong (by looking at the error logs on my site :-)). In essence I had to increase the values of memory_limit and php_value_memory_limit in my PHP.ini file. I set them both to 128M and I can now Load all posts from within Live Writer.
Just for further reference I was seeing:
AH01215: PHP Fatal error: Allowed memory size of 50331648 bytes exhausted (tried to allocate 280291 bytes) xxxx
Being logged when I was using Live Writer to try and load more than 20 posts.
Thanks